It’s no surprise that financial gain can be a powerful motivator, but a variety of groups are using that knowledge in innovative ways to help people get healthier.

Mayo Clinic researchers recently reported that participants in a weight-loss study who had the opportunity to lose or gain $20 a month lost an average of 9 lb. in a year, which was four times greater than the amount lost by those who didn’t have the financial incentive. Another study published in April in the Annals of Internal Medicine reported that cash also motivates groups of people to lose weight together by tying each dieter’s progress to the group’s potential winnings.

Employers are also catching on, and companies are increasingly incorporating cash incentives into their office wellness programs in an effort to reduce costly health care bills for preventable diseases. In 2009, for example, General Electric Co. offered a $750 cash incentive to its workers to stop smoking. About 15% were able to quit for a year, which was three times longer than a comparison group without the cash reward was able to remain smoke-free.

But even beyond pay-to-be-well programs, new apps are capitalizing on the reward concept in innovative ways to promote healthy behaviors and motivate patients. Tyler Thompson, a 25-year-old from LaGrange, Ga., is hooked on the motivation and incentives provided by the LifeKraze app. Thompson was born with spina bifida and is wheelchair-bound, but LifeKraze, which looks similar to a Twitter feed, allows him to post his weekly achievements, like competing in local 5K races, and to see what other members have accomplished as well. LifeKraze users gain points from other members as praise and can earn discounts on fitness products or make donations to nonprofits. Each week, users also receive 300 points to distribute to people they follow to encourage them on their accomplishments (similar to Facebook likes).

“It’s not fun a lot of the times [having spina bifida], but I can feel good through the encouragement [of] others, [and] it makes me want to continue,” says Thompson, who hopes to one day be able to compete in a 10K.

“We’ve seen a lot of research that proves that without a support system, there’s a high failure rate,” says Jay Kelley, president of LifeKraze which was created the app as a social community to motivate people to make themselves better through their health and fitness initiatives from simply eating healthy, to training for a marathon. “If you entirely rely on your own will power and you experience some kind of setback, it is hard to rally from that. With this community with support, we provide the mechanism people need to keep going wherever they are.”

And even if things don’t turn out as expected, these programs can still do good. Last week PayPal co-founder Max Levchin and former Google executive Mike Huang launched a fertility app called Glow, which helps women identify their optimal time for getting pregnant, based on their ovulation and menstruation-cycle data. Women log their data, like temperature, mood and cervical-mucus status, and the app crunches their stats to determine their optimal period of fertility. Users can also sign up for Glow First, which is a nonprofit program that costs $50 a month; if a woman does not get pregnant during the first 10 months of using Glow, money from the fund is equally divided among patients who signed up in the same period and were unsuccessful, and sent to the fertility clinic of their choice to help pay for their treatments.

But it’s not just the current users who might benefit from the app. As Financial Times reporter April Dembosky writes, the app allows the folks behind Glow to gain good-quality data from women — on ovulation cycles and pregnancy outcomes — that could become the basis for algorithms used by insurers to assess risk and premiums for health care services. It’s still not clear whether enough people will sign up for the app to produce robust-enough data to attract the interest of insurance companies, which already collect this type of information, but it’s an intriguing way of thinking about how to collect health data and where it might be applied.

So while tempting people with cash sounds like a crass way of promoting healthy behavior, money talks, and in this case, it’s telling people how to live better.